Mobile terminals such as tablet terminals and tablet PCs include antennas and television tuners, and thus the mobile terminals may directly receive (hereinafter, referred to as “air-reception”) television broadcasts using the antennas (See PTL 1). For example, if terrestrial digital broadcasts (full segment/one segment) and multimedia broadcasts for mobile terminals are intended to be received, television broadcasts can be received in the outdoors, and thus the convenience of the mobile terminals can be improved.
When tuners are mounted on the tablet terminals, it is desirable to automatically select an antenna having a highest quality among the provided antennas in a going-out destination. For example, it is assumed a case where an earphone antenna is connected with an intention to listen to audio when as well a rod antenna is connected without being extended. With the user not being aware, the tuner determines that the earphone antenna is most suitable through an automatic determination, and thus viewing is possible with the earphone antenna. Of course when an earphone or a cable is not connected, switching to the rod antenna is performed.
On the other hand, when the user returns home, reception through a connection with an antenna terminal that has reached the wall is more stable than continuing reception with the antenna. In this case, it is desirable that an F-type connector be provided in a cradle and connection through a cable be possible. Further, by adding such a function, a lifestyle such as recording programs while charging during the time the user is at home and viewing at a going-out destination is possible. Likewise, it is desired to realize optimum television viewing by automatically switching an antenna in both the going-out destination and indoors.
There is a method in which a plurality of antennas are provided, and the antennas are switched in a real time manner so as to maintain good reception state. However, there is a problem in that it is very laborious to detect which antenna can receive a broadcast at the optimum level and to automatically switch antennas, and a switching time becomes long. The antenna switching can be performed manually, but in this case, it bothers the hand of the user operating a mobile terminal. Moreover, in order for the user to select an antenna appropriately, it is necessary for the user to have technical knowledge.
Furthermore, it is possible to receive a television broadcast better by using the antennas provided in homes, apartments or the like, as compared to the antennas with which the mobile terminals are equipped. For example, the antenna terminal (for example, F-type connector) on the wall surface and the node of the mobile terminal are connected through a coaxial cable. If the television broadcast which has been well received is not only viewed but also recorded in the mobile terminal, it is possible to replay and enjoy the program content.
In some apartments, cable television (CATV) has been introduced so as to receive terrestrial digital broadcasts. In CATV, a trans-modulation method and a pass-through method are known as a method of transmitting the terrestrial digital broadcasts. The trans-modulation method is a method of converting received waves by a CATV station into a modulation method suitable for CATV and transmitting converted waves. In the trans-modulation method, it is necessary to connect a Set Top Box (STB) to a television receiver to receive CATV digital broadcasts.
The pass-through method is a method of transmitting received waves without changing a modulation method. Further, an example of the pass-through method includes a same frequency pass-through method of retransmitting the waves of a UHF band used in the terrestrial digital broadcasts without changing the frequency, and a frequency conversion pass-through method of converting the waves into a frequency different from the frequency of broadcast and retransmitting the converted waves. In the pass-through method, the STB is not necessary. In a case of the same frequency pass-through method, it is possible to receive a broadcast in a television receiver for receiving a general terrestrial digital broadcast. In a case of the frequency conversion pass-through method, the terrestrial digital broadcast can be viewed in a “CATV pass-through support” television receiver in which the reception range of the frequency after conversion is broadened to a range other than the UHF band. Television receivers, tuners, and the like which are commercially available are mostly “CATV pass-through support” products.
FIG. 1A shows band allocation in Japan. A transmission band of broadband facilities is 90 to 770 [MHz]. This band is divided as follows:
VHF band (low band) (denoted as VHF-L) (90 to 108 [MHz])
Mid band (denoted as MID) (108 to 170 [MHz])
VHF band (high band) (denoted as VHF-H) (170 to 222 [MHz])
Super-high band (denoted as SHB) (222 to 468 [MHz])
UHF band (denoted as UHF) (470 to 770[MHz])
In a case of the frequency conversion pass-through method, it is possible to transmit a television broadcast by using, for example, a super-high band. Accordingly, the “CATV pass-through support” products are intended to receive all the above described bands (90 to 770 [MHz]). The super-high band is allocated to other applications in a case of radio waves, but since the super-high band becomes an interfering factor at the time of air-reception, it is necessary to block the reception of the super-high band by using a filter.
In a case of the terrestrial analog broadcasts in the related art, as shown in FIG. 1B, frequency bands of VHF-L (1 to 3 channels), VHF-H (4 to 12 channels), and UHF (13 to 62 channels) have been used. As shown in FIG. 1C, since the terrestrial digital broadcast uses UHF (13 to 52 channels) band, in a case of the air-reception of the terrestrial digital broadcast, the UHF may be able to be received.
In recent years, the provision of multimedia broadcasts for mobile terminals has started using a part (207.5 to 222 [MHz]) of the band of VHF-H of the terrestrial analog broadcasts that is obsolete. One of the standards of the multimedia broadcasts for a mobile terminal is Integrated Services Digital Broadcast Terrestrial Mobile Multi-Media Broadcast (ISDB-Tmm). ISDB is a method for digital broadcast that has been adopted in Japan, the Philippines, and Latin America. A family of ISDB includes, in addition to ISDB-Tmm, ISDB-S for satellite digital broadcasts, ISDB-T for terrestrial digital broadcasts, ISDB-TSB for terrestrial digital audio broadcasts, ISDB-C for digital cable television, and the like.